Gas pilot system and method having improved oxygen level detection capability and gas fueled device including the same

ABSTRACT

A pilot system including a pilot including a nozzle and a light sensor adjacent to the nozzle. The light sensor determines whether or not the pilot flame is in a predetermined position relative to the nozzle.

BACKGROUND OF THE INVENTIONS

[0001] 1. Field of Inventions

[0002] The present inventions relate generally to gas pilots and, more particularly, to the oxygen level detection systems associated with gas pilots.

[0003] 2. Description of the Related Art

[0004] Gas pilot systems are associated with a wide variety of gas fueled devices. Such devices include, but are not limited to, vented gas heaters, which include pipes or conduits that are used to vent exhaust to the atmosphere, vent-free gas heaters, vented and vent-free gas log heater, vented and vent-free fireplace systems, water heaters, vented and vent-free stoves, and ovens. The most common types of gas fuel are natural gas and propane. A gas pilot system typically includes an ignition device, such as an electrode, and a pilot having a small nozzle. A pilot flame is formed when gas from the nozzle is ignited by the ignition device. The pilot flame is then used to ignite the gas that is supplied to the burner(s) of the gas fueled device during use.

[0005] The level of oxygen in the air is typically about 20.9%. It is important that the oxygen level in a room in which a gas fueled device is used remain at or near 20.9%, both for proper combustion and safety purposes. An adequate supply of fresh air will maintain the oxygen level at or near the desired level. In buildings with loose structures, such as houses made of wood, an adequate supply of fresh air will enter via wall spaces as well as door and window frames. Other buildings are more tightly sealed. Here, steps should be taken to insure that fresh air is supplied.

[0006] Unfortunately, some rooms do not receive an adequate supply of fresh air. Thus, for safety purposes, many gas fueled devices include an oxygen depletion sensor system (“ODS system”) which will automatically shut off the flow of gas to the pilot and burner when the oxygen level in the air drops below a predetermined “unsafe” level (typically below about 18.5%). The ODS systems monitor the pilot flame because the position of the pilot flame relative to the pilot nozzle is indicative of the oxygen level in the room.

[0007] Referring to FIGS. 1A to 1C, conventional ODS systems employ a thermocouple TC to detect the presence of a pilot flame F when it is in the “normal” oxygen level position (oxygen level greater than or equal to 21%) illustrated in FIG. 1A or the “relatively low” oxygen level position (oxygen level between 18.5% and 19.2%) illustrated in FIG. 1B. In either case, gas will continue to flow to the pilot and burner because the voltage generated by the thermocouple TC, and received by the ODS system controller, will be within an allowable range. When the oxygen level drops to an “unsafe” level (oxygen level below 18.5%), the pilot flame F will move to the location illustrated in FIG. 4C. Here, the pilot flame will not be in contact with the thermocouple TC or substantially close to thermocouple TC. As a result, the temperature of the thermocouple TC will drop, as will the voltage produced thereby. The voltage drop will cause the ODS system to cut off the supply of gas to the pilot and burner. As illustrated in U.S. Pat. No. 5,807,098 to Deng, which is incorporated herein by reference, some ODS systems also include a second thermocouple that is used to generate a warning when the pilot flame moves to the “relatively low” oxygen level position.

[0008] Although conventional ODS systems are generally quite useful, the inventor herein has determined that there are also certain disadvantages associated therewith. Most notably, when the level of oxygen in a room is dropping, the pilot flame F will often first bounce back and forth between the “normal” position illustrated in FIG. 1A and the “relatively low” position illustrated in FIG. 1B, and then bounce back and forth between the “relatively low” position illustrated in FIG. 1B and the “unsafe” position illustrated in FIG. 1C. This can go on for a significant period of time. The pilot flame F will, for example, often bounce back and forth between the “relatively low” position and the “unsafe” position for 15 seconds and, during this time, the temperature at the thermocouple TC will not drop to a level low enough to cause the ODS system to cut off the supply of gas to the pilot and burner. As a result, the inventor herein has determined that the conventional methods of monitoring the pilot flame introduce unnecessary delays into the operation of conventional ODS systems.

SUMMARY OF THE INVENTIONS

[0009] A pilot system in accordance with one embodiment of a present invention includes a pilot having a nozzle and a light sensor adjacent to the nozzle. The light sensor determines whether or not the pilot flame is in a predetermined position relative to the nozzle. In a preferred implementation, the light sensor determines when the pilot flame is not in either of the “normal” oxygen level and “relatively low” oxygen level positions, i.e. when the pilot flame is in the “unsafe” oxygen level position.

[0010] There are a number of advantages associated with such a pilot system. Most notably, the light sensor is capable of detecting movement of the pilot flame the instant that the pilot flame first moves to the “unsafe” oxygen level position, even if it quickly bounces back to the “relatively low” oxygen level position. ODS systems employing the present pilot system will, therefore, be able to make an “unsafe” oxygen level determination much more quickly than ODS systems that employ a conventional thermocouple-based pilot flame monitoring arrangement. As a result, ODS systems employing the present pilot system will also be able to, for example, cut off the supply of gas to a pilot and burner much faster than ODS systems that employ a conventional thermocouple-based pilot flame monitoring arrangement.

[0011] The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Detailed description of preferred embodiments of the inventions will be made with reference to the accompanying drawings.

[0013]FIG. 1A is a side view of a conventional pilot system and oxygen depletion sensor with th pilot flame in the “normal” oxygen level position.

[0014]FIG. 1B is a side view of the conventional pilot system and oxygen depletion sensor illustrated in FIG. 1A with the pilot flame in the “relatively low” oxygen level position.

[0015]FIG. 1C is a side view of the conventional pilot system and oxygen depletion sensor illustrated in FIG. 1A with the pilot flame in the “unsafe” oxygen level position.

[0016]FIG. 2A is a side view of a pilot system and oxygen depletion sensor in accordance with a preferred embodiment of a present invention with the pilot flame in the “normal” oxygen level position.

[0017]FIG. 2B is a side view of the pilot system and oxygen depletion sensor illustrated in FIG. 2A with the pilot flame in the “relatively low” oxygen level position.

[0018]FIG. 2C is a side view of the pilot system and oxygen depletion sensor illustrated in FIG. 2A with the pilot flame in the “unsafe” oxygen level position.

[0019]FIG. 3 is a section view of a mixing chamber in accordance with a preferred embodiment of a present invention.

[0020]FIG. 4 is a top view of a portion of the pilot system and oxygen depletion sensor illustrated in FIG. 2A.

[0021]FIG. 5 is a perspective view of a heater in accordance with a preferred embodiment of a present invention.

[0022]FIG. 6 is a partially exploded view of a propane gas heating assembly that may be used in conjunction with the heater illustrated in FIG. 5.

[0023]FIG. 7 is a diagram of a gas fueled system in accordance with a preferred embodiment of a present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.

[0025] As illustrated for example in FIGS. 2A, 3 and 4, a pilot system 10 in accordance with a preferred embodiment of a present invention includes a pilot 12 having a gas/air mixing chamber 14 and a nozzle 16. Gas G enters the mixing chamber 14 through a small gas orifice 18, while air A enters the mixing chamber through a pair of small air orifices 20. The gas/air mixture G/A exits the mixing chamber 14 through an outlet orifice 22. Mixing continues as the gas/air mixture G/A travels through a tube 24 to the nozzle 16. The gas G in the gas/air mixture G/A is ignited by the L-shaped electrode 26 of an ignitor 28 to create the pilot flame F. The inlet and outlet orifices 18 and 22 are preferably formed from a relatively hard material. In a preferred implementation, the orifices are formed in a ruby or other hard precious stone that is mounted in a copper frame.

[0026] The size of the orifices 18 and 20 depends on the fuel being used. For example, when the fuel is natural gas supplied at a pressure of 6 inches of mercury, the orifice 18 is approximately 0.38 mm in diameter and the orifice 18 is approximately 0.46 mm in diameter when the natural gas is supplied at a pressure of 3 inches of mercury. In both cases, the orifices 20 are each approximately 3 mm in diameter. The orifice 18 is approximately 0.22 mm in diameter and the orifices 20 are each approximately 3.2 mm in diameter when the fuel is liquid propane gas supplied at about 8 to 11 inches of mercury. The outlet orifice 22 is approximately 4 mm. The outlet pressure should be about 8 to 11 inches of mercury when the fuel is liquid propane gas and about 3 to 6 inches of mercury when the fuel is natural gas.

[0027] Mixing the gas and air in the manner described above is advantageous because it insures that the level of oxygen in the ambient air will be accurately represented by the position of the pilot flame F, thereby increasing the accuracy of the ODS system described below. Accuracy of the ODS system may also be augmented by controlling movement of the pilot flame F through use of the relationship between the diameter of the pilot nozzle 16, the fuel pressure, the distance of the electrode 26 from the nozzle as well as the location of the electrode relative 26 to the nozzle centerline, and the level of oxygen in the air. In a pilot system for use in conjunction with a propane gas heater such as that illustrated in FIGS. 5 and 6, the diameter of the pilot nozzle 16 is approximately 0.23 mm (+0.005 mm) and the gas pressure is between 8 and 11 inches of mercury. The downwardly extending portion of the L-shaped electrode 26 is offset with respect to the centerline of the pilot nozzle 16 by 3.00 mm and is spaced approximately 3.50 mm from the nozzle. Such an arrangement reduces the speed of gas flow, thereby increasing the duration and effectiveness of gas/air mixing, and also reduces the tendency of the pilot flame F to bounce around, as compared to conventional S-shaped electrodes.

[0028] The exemplary pilot system 10 illustrated in FIGS. 2A, 3 and 4 also includes an oxygen depletion sensor that may be used in an ODS system in the manner described below with reference to FIGS. 6 and 7. The oxygen depletion sensor is preferably a light sensor that senses light from the pilot flame F. Any suitable light sensor may be employed so long as it is capable of detecting the presence and absence of light emitted by the pilot flame F. In the preferred embodiment, the pilot system 10 is provided with an infrared sensing device 30 having a sensing element 32 that is positioned adjacent to the pilot nozzle 16 and pilot flame F. A suitable infrared sensing device is manufactured by Shanghai Infrared Appliances Co., located in Shanghai, China. The pilot flame F generates infrared electromagnetic radiation (i.e.electromagnetic radiation with wavelengths between 750 nanometers and 1 millimeter) which is sensed by the sensing element 32 when the pilot flame is in the “normal” oxygen level position illustrated in FIG. 2A and, in the illustrated embodiment, in the “relatively low” oxygen level position illustrated in FIG. 2B. The infrared radiation causes the sensing element 32 to generate a flame signal which indicates that the flame is in the normal position. Another example of a suitable light sensor is one that senses visible light (not shown), such as those produced by China Wuxi Light Appliances Co, located in Wuxi, China. In the preferred embodiment, the instant that the pilot flame F moves beyond the “relatively low” oxygen level position (oxygen level between 18.5% and 19.2%) illustrated in FIG. 2B to the “unsafe” level position (oxygen level below 18.5%) illustrated in FIG. 2C, the sensing device 30 will stop generating a flame signal which indicates that the pilot flame is in an allowable position. The signal from the sensing device may drop to zero, or simply to a level lower than the expected level, when the pilot flame F moves from the “normal” or “relatively low” oxygen level position to the “unsafe” oxygen level position. Thus, even in those instances where the pilot flame F jumps back and forth between the “relatively low” and “unsafe” oxygen level positions, the present sensing device 30 will immediately indicate that the oxygen level has dropped to an “unsafe” level because it will fail to produce the expected flame signal the first time that the pilot flame moves out beyond of the “relatively low” position to the “unsafe” position.

[0029] As illustrated in FIGS. 2A and 4, the exemplary pilot system 10 may also be provided with a light shield 34 that is positioned above the nozzle 16 around the area that will be occupied by the pilot flame F when the oxygen level is “normal.”The light shield 34, which is preferably opaque, non-reflective and formed from metal, includes a slot 36 that faces the sensing element 32. The light shield 34 prevents the sensing element 32 from being effected by stray light that could result in the expected flame signal when the flame is actually in the “unsafe” oxygen level position. As such, the sensing element 32 will only be effected by the infrared electromagnetic radiation from the pilot flame F which passes through the slot 36 when the pilot flame is in the “normal” and “relatively low” oxygen level positions. In the illustrated embodiment, the light shield 34 is about 7.2 mm in diameter and about 10 mm in length, while the slot 36 is about 3.6 mm wide.

[0030] In an alternative embodiment (not shown), the components may be reconfigured such that the sensing device 30 will stop generating a signal which indicates that the pilot flame F is in an allowable position the instant that the pilot flame F moves out of the “normal” oxygen level position to either the “relatively low” oxygen level position or the “unsafe” oxygen level position. For example, the light shield 34 could be provided with a small hole that faces the sensing element 32 in place of the slot 36 in order to substantially reduce the amount of light from the pilot flame F that will reach the sensing element when the pilot flame moves to the “relatively low” oxygen level position.

[0031] The exemplary pilot system 10 is also provided with a bracket system 38 that fixes the positions of the various elements of the pilot system relative to one another. Referring more specifically to FIGS. 2B and 2C, the exemplary bracket system 38 includes a L-shaped main bracket 40 having a first portion 42 that is mounted on the pilot 12 adjacent to the nozzle 16. The light shield 34 is supported by the first portion 42. The ignitor 28 and sensing device 30 are mounted on a second portion 44 of the main bracket 40 and are fixed in place by a clamp 46. The clamp 46 may be secured to the main bracket 40 with a screw 48 or other suitable fastening device. A pair of mounting apertures 50 and 52 are formed in the main bracket 40 so that the pilot system 10 may be easily mounted within a gas fueled device. In the illustrated embodiment, the end of the sensing element 32 is about 20 to 22 mm from the nozzle 16 and about 26 to 36 mm above the nozzle (measured with the system 10 oriented such that the pilot 12 extends vertically).

[0032] Although not so limited, heaters are one example of a gas fueled device in accordance with the present inventions. An exemplary heater 100 is shown in FIG. 5. Such a heater may be fueled by natural gas, propane gas or other appropriate fuels. The exemplary heater 100 includes a housing 102 mounted on a base 104. The housing 102 includes a heating chamber 106 which contains a plurality of heat emitting ceramic infrared burner plaques 108 and is covered by a grill 110. The housing 102 also includes a plurality of air circulation vents 112 and 114, as well as a pair of handles 116. Air enters the housing through vent 112 and exits through the heating chamber grill 110 and the vent 114.

[0033] The heater controls are located on the top portion of the housing 102 in the exemplary heater 100. These controls include an ignition knob 118, a temperature setting knob 120 that is used when the heater is in the thermostatic control mode, and a burner control knob 122 that is used to select the number of burners to which fuel will be supplied. The exemplary ignition knob 118 includes OFF, IGNITE, PILOT and ON settings. The temperature setting knob 120 includes a plurality of numbered settings, each corresponding to a desired amount of heat output.

[0034] As shown by way of example in FIG. 6, a propane gas-fueled heating assembly that may be used in conjunction with the housing 102 shown in FIG. 5 includes five burners 124, each of which consists of an infrared ceramic plaque 108 that is secured to a corresponding burner box 126. The number of burners may, however, be increased or decreased to suit particular applications. An upper burner deflector bracket 128 and lower burner deflector bracket 130 are also shown. Propane gas is supplied to the burners and pilot system in the following manner.

[0035] Referring to FIGS. 6 and 7, the gas enters the heating assembly through a pressure regulator 132 and an inlet pipe 134. From there, it enters a thermostat and valve control system 136. The exemplary control system 136 includes an electronic controller 138 such as a control circuit, microcontroller, microprocessor or other suitable control apparatus. The ignition knob 118 and temperature setting knob 120 are connected to the controller 138. No gas will pass beyond the control system 136 when the ignition knob 118 is set to the OFF mode. To place the heater in the pilot mode, the ignition knob 118 is moved from the from the OFF position, past the IGNITE position to the PILOT position. The controller 138 will cause a valve 139 to open and allow gas to pass through a gas line 140 to the pilot 12. The ignitor 28, which is connected to the control system 136 by a wire 142, ignites the gas/air mixture to form the pilot flame F. As noted above, the pilot flame F is monitored by the sensing device 30. Signals from the sensing device 30 are provided to the control system 136 by a wire 143.

[0036] Suitable commercially available thermostat and valve control systems include Mertik Maxitrol GmbH (located in Thale, Germany) Model No. GV31-A₁A₂A₉HOI; Copreci, S. Coop. (located in Aretxabaleta, Spain) Model Nos. VT-23100/13 and VT-23100/ET093-01; SIT Ia precisa, s.p.a (located in Padova, Italy) Model Nos. EUROSIT 0.630.535 and EUROSIT 0.630.545; and Nan Jia Electric & Gas Products Co. Ltd. (located in Nan Jing, China) Model Nos. WHED09001, WHEF09002, WEEF09004, WEED09003 and WEHE09005.

[0037] After the pilot flame F is lit and appropriate signals from the sensing device 30 are received, the controller 138 will maintain valve 139 in the open position and also cause valve 141 to open, thereby allowing gas to be supplied to the burners through a gas line 144 and a gas control valve 146. The amount of gas supplied to the burners 124 is mechanically regulated by the thermostat and valve control system 136 and valve 141 and is equal to that necessary to maintain the temperature specified by the temperature setting knob 120. The temperature is monitored by a thermocouple 148 which is connected to the control system 136 by a line 150. The burner control knob 122 in the exemplary embodiment has five settings, OFF, PILOT/IGNITE, LOW, MEDIUM and HIGH, each of which corresponds to a control valve 146 state. No gas is supplied to the burners 124 by the control valve 146 when the control knob 122 is set to OFF or PILOT/IGNITE. When the control knob 122 is set to LOW, MEDIUM or HIGH, gas will be supplied to one, three or five of the burners, respectively, through gas lines 152, 154 and 156.

[0038] It should be noted that if, for example, a three burner design is employed, then the corresponding progression could be one, two or three burners. It should also be noted that heaters in accordance with the present invention may also be cond in such a manner that the burner control knob 122 and control valve 146 are both eliminated. When such a configuration is employed, all of the burners will be used whenever the heater is in operation and the amount of gas supplied to the burners will be controlled by the thermostat control valve. Ignition functions may be handled by an ignition switch.

[0039] Turning to oxygen level detection, the sensing device 30 and controller 138 form an ODS system that may operate in the following manner. As noted above, the instant that the pilot flame F moves beyond the “relatively low” oxygen level position (oxygen level between 18.5% and 19.2%) illustrated in FIG. 2B to the “unsafe” oxygen level position (oxygen level below 18.5%) illustrated in FIG. 2C, the sensing device 30 will stop generating a flame signal which indicates that the pilot flame is in an allowable position. The controller 138 will, as a result, immediately close the valve 139 that allows gas to pass to the pilot 12 and also close the valve 141 that allows gas to pass to the burners 124 (if the valve 141 has been opened). The heater 100 may, if desired, be provided with an audio and/or visual alarm that is triggered by the controller 138 the valves 139 and 141 are closed by the controller in response to an “unsafe” oxygen level detection.

[0040] Although the present inventions have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. By way of example, but not limitation, the present inventions may be incorporated in heaters which do not have a thermostatic control system. The “unsafe,” “low” and “normal” oxygen level percentages discussed above may be varied if desired. The exemplary pilot system may also be incorporated into other gas fueled devices such as water heaters, stoves, ovens and other types of heaters. The pilot, sensing device and controller could also be reconfigured and repositioned such that the sensing device senses the flame when it is in the “unsafe” oxygen level position and this sensing results in closure of the gas valve(s). It is intended that the scope of the present inventions extends to all such modifications and/or additions. 

I claim:
 1. A pilot system for generating a pilot flame, comprising: a pilot including a nozzle; and a light sensor adjacent to the nozzle.
 2. A pilot system as claimed in claim 1, wherein the light sensor comprises an infrared light sensor.
 3. A pilot system as claimed in claim 1, further comprising: a ignitor positioned adjacent to the nozzle; wherein the light sensor faces a region located between the nozzle and the ignitor.
 4. A pilot system as claimed in claim 1, further comprising: a light shield substantially surrounding the nozzle and defining an open region that faces the light sensor.
 5. A pilot system as claimed in claim 1, further comprising: a mixing chamber located upstream of the nozzle including a gas inlet, an air inlet and a gas/air mixture outlet in communication with the nozzle.
 6. A pilot system as claimed in claim 1, wherein the pilot is constructed such that the pilot flame will be located in a first position in response to a first oxygen level and a second position in response to a second oxygen level, the second oxygen level being less than the first oxygen level, and the light sensor will receive a level of light indicative of an allowable oxygen level when the pilot flame is in the first position and will not receive a level of light indicative of an allowable oxygen level when the pilot flame is in the second position.
 7. A gas fueled device, comprising: a burner; a pilot including a nozzle associated with the burner; and a light sensor adjacent to the nozzle.
 8. A gas fueled device as claimed in claim 7, wherein the burner comprises a ceramic plaque.
 9. A gas fueled device as claimed in claim 7, wherein the light sensor comprises an infrared light sensor.
 10. A gas fueled device as claimed in claim 7, further comprising: a ignitor positioned adjacent to the nozzle; wherein the light sensor faces a region located between the nozzle and the ignitor.
 11. A gas fueled device as claimed in claim 7, further comprising: a light shield substantially surrounding the nozzle and defining an open region that faces the light sensor.
 12. A gas fueled device as claimed in claim 7, further comprising: a mixing chamber located upstream of the nozzle including a gas inlet, an air inlet and a gas/air mixture outlet in communication with the nozzle.
 13. A gas fueled device as claimed in claim 7, wherein the pilot is constructed such that the pilot flame will be located in a first position in response to a first oxygen level and a second position in response to a second oxygen level, the second oxygen level being less than the first oxygen level, and the light sensor will receive a level of light indicative of an allowable oxygen level when the pilot flame is in the first position and will not receive a level of light indicative of an allowable oxygen level when the pilot flame is in the second position.
 14. A gas fueled device as claimed in claim 13, further comprising: a gas inlet operably connected to the pilot; and a control device operably connected to the light sensor that prevents gas flow from the gas inlet to the pilot when the light sensor does not receive a level of light indicative of an allowable oxygen level.
 15. A gas fueled device as claimed in claim 13, further comprising: a gas inlet operably connected to the burner; and a control device operably connected to the light sensor that prevents gas flow from the gas inlet to the burner when the light sensor does not receive a level of light indicative of an allowable oxygen level.
 16. A method of monitoring a pilot flame produced by a gas pilot, comprising the steps of: determining whether light is being emitted from a predetermined region associated with the pilot; and preventing gas flow from flowing to the pilot in response to a determination that light is not being emitted from the predetermined region.
 17. A method as claimed in claim 16, wherein the step of determining whether light is being emitted comprises determining whether infrared light is being emitted from a predetermined region associated with the pilot.
 18. A method as claimed in claim 16, wherein the gas pilot includes a nozzle and an igitor defining a region therebetween and the step of determining whether light is being emitted from a predetermined region comprises determining whether light is being emitted from the region between the nozzle and the ignitor.
 19. A method as claimed in claim 16, wherein the step of preventing gas flow from flowing to the pilot comprises closing a valve.
 20. A method as claimed in claim 16, wherein the gas pilot includes a nozzle, the method further comprising the step of: mixing gas with ambient air to form an air/gas mixture; and providing the air/gas to the nozzle. 